Re: Those Programs...

That happened on older features phones... And I don't really know the purpose that those programs had because actually the only thing that they did (or as far as I knew) was erasing all the phone's information or locking, making the UI go all crazy or stuff like that.Due to the limited data-transferring capabilities that those phones had I really doubt that those viruses were really dangerous.Besides, you had to accept and open a file in order to activate a virus.

For modern smartphones... You can disguise the spy-ware as an update or inside another application like a game. It will be installed by the user, as well as the other guy said, you can take the phone for a while and install it yourself from your computer.